Biomechanical evaluation of connectible skills using iliac screw and lumbar-sacral spine pedicle screw in the fixation between lumbar-sacral spine and pelvis

Rukun SU; Xingmo LIU; Yinghui DENG; Fobao LI; Tao PAN

ABSTRACT

BACKGROUND:

There have been many methods of fixation between lumbar-sacral spine and pelvis. However, a safe, firm, and ideal method of internal fixation has not been found.

OBJECTIVE:

This study was designed to investigate the stability of the fixation between lumbar-sacral spine and pelvis with the connectible skills using iliac screw and lumbar-sacral spine pedicle screw.DESIGN, TIME AND

SETTING:

This study, a control experiment, was performed at the Institute of Biomechanics, Sun Yat-sen University, Guangzhou, Guangdong Province, China between January 2006 and December 2007.MATERIALS The lumbar-sacral spine and pelvis specimens were collected from six freshly cryo-preserved male adult corpses caused by trauma. Iliac screw (8.5mm×100mm), L5 pedicle screw (6.5mm×45mm), and S1 pedicle screw (6.5mm×35mm) were provided by Sofamor Company, USA. MTS 858 Bionix Material Testing System (USA) was also used.

METHODS:

The lumbar and iliac vertebrae, pelvis from six fresh frozen cadaveric specimens were operated in three different ways of fixation respectively iliac ala lag screw, L5-S1 pedicle screw rod system, iliac screw and L5 pedicle screw connecting system. Three ways of fixation as mentioned above were compared with the intact group in biomechanical stability.MAIN OUTCOME

MEASURES:

The mobility of whirl, lateral bending, proneness, and backward stretching among groups.

RESULTS:

Using iliac screw for the fixation between lumbar-sacral spine and pelvis turned out to be the best in stability. The range of motion (ROM) decreased obviously in each situation. The three-dimensional mobility in the 6.4Nm moment of force was (1.07±0.86)° for whirl, (0.95±0.47)° for lateral bending, (1.22±0.67)° for proneness, and (1.80±0.73)° for backward stretching. There was significant difference between the intact group and the group carried out by iliac screw and L5 pedicle screw for the fixation between lumbar-sacral spine and pelvis (P<0.01).

CONCLUSION:

The connectible skills using iliac screw and the lumbar-sacral spine pedicle screw possesses the biomechanical advantages of maintaining the stability between lumbar-sacral spine and pelvis.